So really weird thing that happens. Say I am driving 60mph down a highway- my car will do this deep vibrating shaking for like 5 seconds........then it will be a smooth ride for about 10 seconds.......then back to the 5 seconds of deep vibrating. I just can't think of what would be causing such a rhythmic problem. Any ideas?

JimD

04-12-05, 06:51 PM

Are you prepared for a lengthy diagnostic process? There are so many pieces rotating!

Tire pressure?

Lift the car and loosen each wheel lug nuts and torque them back to 100 lb ft in the proper sequence. Consider changing the wheel to hub mating position by one or two bolt holes.

These are only two items on a long checklist that are easy and inexpensive to perform, and should be eliminated as possible causes early in the process.

Good luck with it!!

Fritzi

04-12-05, 07:06 PM

Well, I am actually going to be putting my summer 20'' wheels on in a week or so , so I will go for it then and see how it works. Thanks

mcowden

04-12-05, 10:36 PM

It could be a wheel out of balance or a broken cord in a tire, maybe a wheel bearing, all sorts of things. Try the previous suggestions from JimD first, then if it continues after you put on your second set of wheels you know it wasn't a wheel and should start looking at bearings and stuff under the hood. My money is on a balance or broken cord problem, though. I had that problem and the symptom was the same. I found it when my right rear tire blew out and when I put the spare on the vibration went away. When I had the tire replaced, they said it had a bad cord. There was no way to know by looking at or feeling the tire until it got bad enough that it blew out. It would really help if you could isolate it to one corner. When did it start? After you hit a really nasty pothole or a curb?

Fritzi

04-12-05, 11:36 PM

Not that I can think of right off the top of my head.

eldorado1

04-12-05, 11:46 PM

Decision tree:

1. Does it occur most often when you're turning?

If so - wheel bearing. Goto Done.

If not - get your tires balanced. Goto Done.

Done.
http://cadillacforums.com/forums/images/smilies/thumbsup.gif

Fritzi

04-12-05, 11:50 PM

Only when I am going straight.

May need to get the wheels balanced, but why would it just come out of no where?

dkozloski

04-13-05, 01:12 AM

I had a Mazda RX-7 that did exactly as you describe. The problem was dynamic balance in the front tires that cycled around because the circumferance of one tire was slightly more than the other so it rotated slightly slower. The imbalance of the two tires would phase in and out and the vibration would come and go as the vibration added and subtracted. It would speed up when going around a sweeping turn which magifyed the rotation speed difference.

mcowden

04-13-05, 12:45 PM

Only when I am going straight.

May need to get the wheels balanced, but why would it just come out of no where?

It's possible that a weight came off the wheel, leaving it unbalanced. Those little lead weights are just hanging on by a slight clamping force and they can come off fairly easily if they weren't perfectly installed or if the clip wasn't very strong. It can also happen if you brush up on a curb just right. I agree that it sounds very much like an unbalanced wheel. If they balance them and they are fine, my next suspicion would be a broken cord. A wheel bearing could do it too, but you'd usually notice a growling sound or something similar instead of just a vibration.

Eldorado1 said "Decision tree:

1. Does it occur most often when you're turning?

If so - wheel bearing. Goto Done.

If not - get your tires balanced. Goto Done.

Done."

Are you a computer geek, too? This reminds me way too much of DOS batch files or shell scripting...